1. Field of the Invention
This invention relates to both novel and known sulfonyl carbazates as well as their use in the art of manufacturing cellular polymeric materials. In particular, sulfonyl carbazates have been found especially useful as chemical blowing agents in the expansion of polymers. The chemicals of the invention are particularly valuable in the expansion of polymers such as elastomers and plastics which are normally processed at elevated temperatures and especially in plastics which are processed at temperatures above 225.degree. C. Particular chemicals herein are even useful at expansion temperatures in excess of 250.degree. C.
The sulfonyl carbazate compounds of this invention contain at least one chemical group of EQU --SO.sub.2 --NHNH--COO--
wherein the oxygen and the sulfur each attach to a various organic group, as hereafter described.
2. Description of the Prior Art
The use of certain monofunctional aryl sulfonyl carbazates of the structure ##STR1## where X is H, CH.sub.3, OCH.sub.3, CH.sub.3 --CO--NH--, Cl, Br, or NO.sub.2 in medicinal preparations, as wetting and lubricating agents, in the textile industry, in the dye industry, as herbicides, and as sedatives has been known from such articles as Zhurnal Organicheskoi Khimii, Vol. 7, No. 4, pp. 794-798, April 1971, J. Chemical Society (c) 1970 (org.) 2629, and Current Science #11, 1966, p. 283-4. However, none of these references has any suggestion of the usefulness of these compounds as blowing agents, nor is there any suggestion or disclosure of polyfunctional or secondary-alkyl substituted sulfonyl carbazates, the new compounds of this invention.
Blowing agents which decompose at relatively high temperatures are not new. U.S. Pat. No. 3,235,519 discloses using sulfonyl semicarbazides as blowing agents for polymeric materials which soften above 170.degree. C. These blowing agents are particularly suitable for expanding high density polyethylenes, and many other rubbery and plastic polymers, but they are unsuitable for expanding certain polymers because they produce ammonia gas upon decomposition, which tends to attack some polymeric materials such as polycarbonates and polyesters, and, in some instances, to react with the metals used for the construction of molding equipment.